Device and method for sensing brightness

Abstract

A device and a method for sensing brightness, by which a sensing area for measuring the brightness of an object is varied. The variation of the brightness sensing unit is in response to the variation of an image angle that varies according to the zoom position of the lens of a zoom camera. In this manner, photographs with optimum exposure can be obtained. The device comprises a zoom position sensing unit, a brightness sensing unit, and a control unit.

What is claimed is: 
     
       1. A brightness sensing device, by which a brightness sensing area of a camera is varied, comprising: a zoom position sensing unit which senses the position of a lens displaced according to a zooming operation and outputs an electrical signal corresponding to the sensed position;   a brightness sensing unit which is divided into a plurality of concentric rectangular cells, and wherein the brightness measuring unit measures the brightness applied to a cell and outputs an electrical signal corresponding to the measured brightness, the brightness sensing unit further including: a central part which is divided into a plurality of concentric circular sensors for performing the functions of back light compensation and automatic flash exposure control under back light conditions, and wherein the circular sensor with the largest area is smaller than the rectangular cell with the smallest area; and   a control unit which detects the position of the lens by the signal outputted from the zoom position sensing unit, and wherein the control unit: selects one cell of the plurality of rectangular cells of the brightness sensing unit, the selected rectangular cell corresponding to the sensed position, to set the exposure value according to the sensed position of the lens; and   outputs a driving signal to drive the selected cell.       
     
     
       2. A device as recited in claim 1, wherein the control unit selects one cell of the plurality of cells such that the area of the selected cell corresponds to the value of a variable multiplied by the film size of the camera. 
     
     
       3. A brightness sensing method in which a brightness sensing area of a brightness sensing unit is varied, comprising the steps of: detecting a current zoom position of a lens when a zooming operation is carried out;   selecting a brightness sensing area of the brightness sensing unit according to the detected zoom position, the brightness sensing unit having a plurality of concentric rectangular cells and a plurality of concentric circular sensors, such that the circular sensor with the largest area is smaller than the rectangular cell with the smallest area;   selecting one of the circular sensors to perform the functions of back light compensation and automatic flash exposure control under back light conditions; and   driving a selected cell of the brightness sensing unit, the cell corresponding to the selected brightness sensing area, to measuring the brightness of an object.   
     
     
       4. A method as recited in claim 3, further comprising the steps of: detecting when the current zoom position corresponds to a wide angle stage, and selecting a cell which has the largest brightness sensing area to be driven to measure the brightness of an object; and   detecting when the current zoom position corresponds to a photo angle stage, and selecting a cell which has a smaller brightness sensing area than that selected in the wide angle stage.   
     
     
       5. A device as recited in claim 1, wherein the control unit selects one of the plurality of circular sensors on the basis of which rectangular cell is selected. 
     
     
       6. A method as recited in claim 4, further comprising the step of selecting one of the plurality of circular sensors on the basis of which rectangular cell is selected.